1. Field of the Invention
The present invention relates generally to an apparatus for examining electrodes of a plasma display panel comprised of a plurality of electrodes for defects, and more particularly to a method and apparatus for examining plasma display panel electrodes using frequency characteristics, which can rapidly and inexpensively examine the electrodes for defects and detect the positions of defective electrodes by detecting frequency characteristic variation due to the generation of defects, such as disconnection and short of the electrodes.
2. Description of the Related Art
A Plasma Display Panel (PDP) is a flat panel display unit based on a gas discharge phenomenon, and has advantages in that it occupies a narrow space, has a wide viewing angle and light weight, and it easily implements various colors. Therefore, the PDP has been recognized as favorable one of devices for High Definition Televisions (HDTVs) and wall-mounted multimedia display apparatuses. Moreover, recently, with the increase of the size of display units, demands for PDPs have increased. Especially, since the PDP has a thickness equal to or less than 4 inches with respect to a screen size of 20 to 80 inches, the PDP is not restricted by space when it is installed. Thus, it is expected that demands for the PDPs will further increase.
Generally, a PDP comprises upper and lower panels combined with each other, a fluorescent material and electrodes printed on the panels. Further, since the PDP is designed in such a manner that each of the panels has a plurality of electrodes to obtain high resolution on a large screen and the sizes of the electrodes are very small, there is a higher danger of damage to the electrodes.
For example, in the case of a HDTV-level PDP, the number of horizontal electrodes is 5760, the number of vertical electrodes is 1080, and each of the PDP electrodes has a width of several hundred μm and a thickness of several hundred nm to several μm.
Moreover, since a high voltage of approximately 200V is applied to the PDP electrodes, the progress of damage to the electrodes is very fast even though only part of the electrodes are damaged.
Further, after the upper and lower panels are combined with each other, maintenance is difficult even though defects are found in the electrodes, so the assembled PDP itself must be discarded.
Therefore, in order to reduce production costs and improve quality of products when PDPs are produced, it is required that the PDP electrodes are examined for defects before the upper and lower panels are assembled to be combined.
A conventional PDP electrode examination method uses a vision system comprised of a plurality of line scan cameras and frame grabbers arranged in parallel to correspond to the size (width) of a target PDP. After upper and lower panels of the PDP are combined with each other, actual screen information, generated when a voltage is applied to PDP electrodes, is scanned by the plural line scan cameras to examine the electrodes for defects. Such a conventional examination method is disadvantageous in that, since the number of line scan cameras is in proportion to examination resolution and the size of the target PDP, system costs and examination time increase as the examination resolution and the size of the target PDP increase.
More specifically, the line scan cameras, which are core components of the vision system, each have a predetermined number of pixels. Currently, a maximum data output speed of the line scan cameras is 100 MHz, and a maximum examination speed per line thereof does not exceed 100 KHz. If such line scan cameras are used, the vision system requires an examination time above several tens of seconds per 40-inch PDP. Meanwhile, in the vision system, since the amount of output data is proportional to the examination resolution or the size of the target PDP, the examination time increases if the examination resolution or the size of the target PDP increases.
Further, in order to examine a large-scale PDP at high resolution, a vision system comprised of line scan cameras with high speed and high resolution is required. However, a line scan camera with high speed and high resolution is very expensive at the present time as much as several tens of million Korean Won.
Therefore, in the case of the vision system, in order to increase resolution by two times, an examination time must increase by four times or the number of line scan cameras must increase by two times. Thus, the vision system is problematic in that, when the PDP electrode examination is carried out using the vision system, an examination time or examination cost increases if the examination resolution or the size of the target PDP increases.
Besides the method using the vision system, there are methods using a magnetic sensor, a roller probe, an Integrated Circuit (IC) probe and the like. These methods are disadvantageous in that, since all of the methods perform examination while moving a sensor or probe on a PDP, a scan area increases with the increase of a PDP size to increase an examination time, and PDP electrode regions may be damaged due to the contact with the sensor or probe.